'Sickle' (ii) was the Allied overall designation of the US build-up of air power in the UK for the Allied air offensive against Germany within the overall context of 'Bolero' (1942/43).

The programme was slow to get under way as its priority was relatively low and diversions were often made, for example two groups of Boeing B-17 Flying Fortress heavy bombers being reallocated to Major General James H. Doolittle’s (from 1 March 1943 Major General Carl A. Spaatz’s) US 12^th AAF in North Africa during 1943, and one group of Consolidated B-24 Liberator heavy bombers to Lieutenant General George C. Kenney’s US 5^th AAF in the South-West Pacific Area during the late summer of 1943.